1. Field of the Invention
This invention relates to the field of spark plugs for internal combustion engines in general, and in particular, to a spark plug for injecting additional air and unburned gases from prior combustions into a cylinder prior to each ignition in order to enhance subsequent combustions.
2. Prior Art
In the operation of internal combustion engines, one very significant problem is the inability to effect a complete burning of the air-fuel charge delivered by the carburetor or fuel injectors into the combustion cylinder. It is known that when a vacuum-balancing quantity of any combustion promoting gas, such as oxygen or air, is introduced into the combustion chamber prior to the ignition of the air-fuel charge, a reduction or complete elimination of the need for the piston to act against the progressive vacuum in the cylinder results. The decrease in the amount of energy expended by the piston as a result of the gas injection has at least two positive advantages. Firstly, there is an increase in gas mileage because effective horse power is increased. Secondly, a more complete combustion of the air-fuel mixture reduces the emission of pollutants during the exhaust stroke of the engine. Other advantages can also arise if the engine burns oil or is required to run on a high octane fuel. In the case of the former, oil deposits in the engine will be significantly reduced, and in the latter case, fuel of lower octane may be substituted.
Notwithstanding an appreciation of the advantages to be gained from injecting additional air into the combustion chamber, a significant problem still remained. Regardless of type of device used to inject additional air or oxygen, the back pressure on the valve mechanism, produced during the compression stroke of the engine, is so great that the valve mechanism is quickly damaged by the shock loads to which it is successively and repeatedly subjected. When the valve assemblies break, the integrity of the combustion cylinder is lost and excessive amounts of fuel can leak out of the engine. Even in relative low compression engines such as those being manufactured today, wherein compression ratios are approximately 8:1, no valve mechanism has been available which could withstand the cyclical shock loading. Even arrangements specifically intended to reduce the back pressure, such as ball-valve assemblies, have proved unsatisfactory due to pressure shock and temperature degradation.
One solution to this problem is fully disclosed in my co-pending application Ser. No. 106,420 entitled AIR INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES, now U.S. Pat. No. 4,325,332. Such an air injection system for injecting air into a combustion cylinder prior to compression, comprises; air inlet means disposed in the spark plug, the air inlet means including a valve means for metering air into the cylinder; a tube connected to the valve means and extending therefrom through the spark plug, being in communication with the cylinder when the spark plug is mounted in an engine; and, a compression chamber surrounding the tube, substantially occupying the interior of the plug, and in communication only with the tube, gases from prior combustions filling the chamber during exhaust strokes, whereby air and gases from prior combustions are injected into the cyinder prior to ignition, and back pressure shock on the valve means is substantially reduced. The hollow tube also serves as a conducting wire, through the spark plug, for the positive electrode.
Although the air injection system disclosed in my co-pending application solves the problems noted above, the cost and complexity of its construction left room for still further improvement. In the spark plug taught herein, the concept of the hollow positive electrode, surrounded by a compression chamber in fluid communication only with the hollow electrode, has been eliminated. The concept of a very large compression chamber has been maintained. Although a solid positive electrode is utilized herein, it nevertheless serves a dual function, as it served a dual function before, in that it provides a guide means and mounting member for a modified valve disk in a modified valve chamber. A spark plug as taught herein is constructed in a modular form, which can be easily disassembled in order to place any broken or worn parts, should that become necessary.